Mastitis is an inflammation of the mammary gland that is caused by bacteria which in most cases enter the gland via the teat orifice. During the non-lactating period or “dry period” in the gland, deposits of keratin in the teat orifice and the streak canal form a primary defense mechanism. A keratin plug that forms in the teat of the animal forms a protective barrier, and the immune-rich tissues of the Furstenbürg's Rosette in the teat, as well as the natural protective factors of the dry-cow secretions, contain high levels of naturally occurring anti-bacterial substances which inhibit the passage of bacteria from the teat orifice to the teat cistern (papillary sinus) and gland cistern. However, this keratin plug and these natural immune defense mechanisms are often overcome by bacterial invasion as the animal is transitioning to the dry period, during the dry period of the animal, and/or during calving. This can result in bacteria invading the gland and causing mastitis during the dry period or, more particularly, immediately following calving.
Products have been developed to seal an animal's teat to prevent mastitis and other conditions. Barrier teat dips are designed for extra-mammary use, to seal the external surface and streak canal of the teat, and are typically used during periods of milking. For heifers, external dip products exist, but none sufficiently seal the teat of the cow externally for a sufficient amount of time to prevent the unique form of mastitis that is so dangerous in heifers. In some heifers and in cows that have experienced one or more pregnancies previously, teat sealants are also used to block or seal the teat canal during the dry period. Furthermore teat sealants are used to plug the teat cistern during the dry period.
U.S. Pat. Nos. 6,395,289 and 6,203,812 to Hydromer teach hydrophilic polymeric blends for use as teat dips during the lactating period. The blends provide barrier properties but can be rapidly removed prior to milking. However, the physical consistency and properties of these teat dips make them unsuitable for teat canal or cistern placement. For example, since these dips do not gel readily, they would tend to not remain in the canal or cistern.
Other teat dip compositions used during an animal's lactating period are disclosed in U.S. Pat. Nos. 4,113,854 and 5,017,369. Applied externally, these compositions form thick films which seal off the end of a teat canal. These compositions include latex and remain viscous and sticky thereby not allowing for teat canal protection from the environmental factors to which the gland is naturally exposed due to its location on the animal. Also, latex may be toxic or irritating to the mammary gland tissues. In addition to the contamination of milk, latex can elicit allergic reactions in humans.
U.S. Pat. No. 5,583,163 to Ciba Geigy and U.S. Pat. No. 5,932,674 to Novartis AG describe methods for the preparation of certain polyvinyl alcohol (PVA) polymers and hydrogels. U.S. Pat. No. 6,652,883 to BioCure teaches the use of PVA based hydrogels as bulking and sealing products. However, the formulations taught in the '883 patent do not have appropriate properties to be useful as intra-canal or intra-teat cistern sealants.
What is needed is a safe formulation that is easy and safe to apply and that preferably forms in place on the tissue. The formed hydrogel has mild adhesion, in the range of 0.05 to 0.5N.